The present invention relates in general to an apparatus for distributing irrigation water, and more particularly to a self-cleaning, drip-type irrigation apparatus for applying water at very low levels.
Heretofore, drip irrigation systems have been used to apply water to crops at much lower levels than would be possible using other methods of irrigation, such as sprinkling and flooding. Although the known drip irrigation systems applied water at much lower levels than the non-drip irrigation systems, they had a tendency to plug up from suspended solids in the water supply, from sucking in dirt when the system was shut down and subsequently draining, and from salt build up in the exterior holes as the water evaporated causing them to plug up. This necessitated the filtration of the water supply, which was a costly procedure. In addition, should silt get into the system, it was difficult to remove.
Manufacturing problems were frequently encountered, since many systems employed restrictive holes for the purpose of controlling the amount of water supplied. The restrictive holes were prone to blockage by suspended solids in the water supply. The restrictive holes also increased in size with use due to erosion of the material surrounding the opening.
The removal of low cost irrigation systems from buried locations after there was no more need for the system in the original location frequently presented a problem. These systems often lacked sufficient internal strength to be removed in tact. This resulted in a twofold increase in costs since the system could not be reused in its entirety and additional expenses were incurred in its removal.
Patents of interest are: U.S. Pat. No. 3,903,929 to Mock for Irrigation Conduit, U.S. Pat. No. 3,698,195 to Chapin for Water Distributing Hose, U.S. Pat. No. 2,798,768 to Babin for Soil Moistening Apparatus, U.S. Pat. No. 3,777,987 to Allport for Irrigation Device, U.S. Pat. No. 3,799,441 to Delmer for Solid Pellet and Self-Cleaning Irrigation Device, U.S. Pat. No. 3,799,442 to Delmer for Fiber Self-Cleaning Irrigation Device. U.S. Pat. No. 2,769,668 to Richards for Irrigation Tubes, U.S. Pat. No. 3,021,642 to Ewing for Lawnmower Attachment for Distributing Liquid, U.S. Pat. No. 3,116,019 to Graef for Irrigating Attachment for a Garden Hose, U.S. Pat. No. 3,667,685 to Rinkewich for Irrigation Devices, U.S. Pat. No. 2,196,456 to Charroin for Group Sprinkling Apparatus, U.S. Pat. No. 2,628,865 to Duncan for Flexible Sprinkler Unit, U.S. Pat. No. 3,693,657 to Olson for Flow Restrictor with Flushing Means, U.S. Pat. No. 3,693,888 to Rondas et al for Fluid Emitter, U.S. Pat. No. 3,729,142 to Rangel-Garza et al for Drippers for Irrigation, U.S. Pat. No. 3,777,980 to Allport for Irrigation Fitting, and U.S. Pat. No. 4,037,791 to Mullett et al for Flow-Control Device.
The Mock patent (U.S. Pat. No. 3,903,929) constitutes the most relevant prior art and discloses an irrigation conduit comprising first and second integral tubes connected by a common wall separating their interiors. A first series of holes extends through the common wall so as to connect the interiors of the tubes. A second series of holes connects the interior of the second tube with the exterior of the conduit. Both the first and second series of holes are obstructed when suspended solids are present in the irrigation water. Filtering the irrigation water prior to its use in the conduit minimizes the obstructions but adds to the costs and is not always feasible.